Reconciling Baja–British Columbia and flat Shatsky conjugate subduction beneath the western United States
Bibliographic record
Abstract
ABSTRACT In this contribution, subduction of the Shatsky Rise conjugate beneath southern California at ca. 90 Ma is reconciled with the presence of Baja–British Columbia (Baja-BC; i.e., Insular superterrane and associated rocks) to the west of North America. The Shatsky Rise, which is currently 1100 km east of Japan, formed due to plume volcanism at the Pacific-Farallon-Izanagi triple junction. We model formation of its conjugate oceanic plateau on the Farallon plate, showing that the conjugate was (despite large ridge jumps) at least 600 km long and 300 km wide. This Shatsky conjugate began subducting beneath southern California at ca. 90 Ma and passed at the base of North America lithosphere from southern California to the Colorado Plateau and to Wyoming at ca. 70 Ma. Evidence includes: removal of the southern Sierra Nevada mantle lithosphere and most of the crust (through both basal erosion and denudation faulting); the emplacement of the Rand schist; the cooling, hydration, and erosion of basal Colorado Plateau and Colorado mantle lithosphere; the creation of Rocky Mountain faulting by the forced NE motion of the Colorado Plateau; and the replacement of Wyoming mantle lithosphere below ~150 km with Shatsky conjugate mantle lithosphere, which is seismically imaged beneath Wyoming and SE Montana. Plutonism in the Mojave Desert until ca. 75 Ma occurred where the Farallon slab sagged off the southern margin of the Shatsky conjugate. The southeast sweep of plutonic extinction and emplacement of the Pelona, Orocopia, and similar schists are attributed to the conjugate of the Ojin Rise Seamount trend of the Shatsky conjugate that swept beneath southern California and SW Arizona. The Shatsky conjugate path would not have intersected with the Insular superterrane if it was proximal to North America and at a relatively northern position within paleomagnetic uncertainty, or if the Insular superterrane was longitudinally separated from North America and ~1000 km offshore of southern California. Therefore, we conclude that Shatsky conjugate flat-slab subduction and northward translation of the Insular superterrane (Baja-BC) are not mutually exclusive hypotheses.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".